<!doctype html>
<html lang="zh-CN">
  <head>
    <!-- 必须的 meta 标签 -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">

	  <link rel="stylesheet" href="bootstrap.css">

    <title>断点</title>
  </head>
  <body>

  <div class="container mt-5"
       style="height: 100px; background-color: #3dd5f3">container</div>

  </body>
</html>